U.S. patent application number 14/529803 was filed with the patent office on 2015-05-07 for developer container, developing apparatus, process cartridge and image forming apparatus.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Toshiya Kaino, Akihisa Matsukawa, Yoshihiro Mitsui, Keisuke Mochizuki, Bunro Noguchi, Shun Sato, Masahiro Shibata, Hisashi Yamauchi.
Application Number | 20150125166 14/529803 |
Document ID | / |
Family ID | 53007138 |
Filed Date | 2015-05-07 |
United States Patent
Application |
20150125166 |
Kind Code |
A1 |
Matsukawa; Akihisa ; et
al. |
May 7, 2015 |
DEVELOPER CONTAINER, DEVELOPING APPARATUS, PROCESS CARTRIDGE AND
IMAGE FORMING APPARATUS
Abstract
Provided is a technology that enhances the detection precision
of the residual amount of a developer. An apparatus according to
the invention includes: an accommodating portion in which a
developer is accommodated; a sheet-like stirring member that, by
rotating, stirs the developer accommodated in the accommodating
portion; a piezoelectric element that is affixed to the stirring
member and that outputs voltage when being deformed; and a
deflection forming portion that comes in contact with the stirring
member, thereby causing the stirring member to deflect, when a free
end of the rotating stirring member is outside a developer
accumulation region in the accommodating portion.
Inventors: |
Matsukawa; Akihisa;
(Fuchu-shi, JP) ; Kaino; Toshiya; (Suntou-gun,
JP) ; Mochizuki; Keisuke; (Suntou-gun, JP) ;
Noguchi; Bunro; (Suntou-gun, JP) ; Sato; Shun;
(Ashigarakami-gun, JP) ; Shibata; Masahiro;
(Numazu-shi, JP) ; Mitsui; Yoshihiro; (Numazu-shi,
JP) ; Yamauchi; Hisashi; (Numazu-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
53007138 |
Appl. No.: |
14/529803 |
Filed: |
October 31, 2014 |
Current U.S.
Class: |
399/27 |
Current CPC
Class: |
G03G 15/0858 20130101;
G03G 15/0889 20130101 |
Class at
Publication: |
399/27 |
International
Class: |
G03G 15/08 20060101
G03G015/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2013 |
JP |
2013-229714 |
Claims
1. A developer container, comprising: an accommodating portion in
which a developer is accommodated; a sheet-like stirring member
that, by rotating, stirs the developer accommodated in the
accommodating portion; a piezoelectric element that is affixed to
the stirring member and that outputs voltage when being deformed;
and a deflection forming portion that comes in contact with the
stirring member, thereby causing the stirring member to deflect,
when a free end of the stirring member is outside a developer
accumulation region in the accommodating portion.
2. The developer container according to claim 1, wherein the
piezoelectric element is affixed to a face, of the stirring member,
on an opposite to a face that comes in contact with the deflection
forming portion.
3. The developer container according to claim 1, wherein the
piezoelectric element is affixed to the stirring member so as to
extend in a direction that is perpendicular to a rotary shaft of
the stirring member.
4. The developer container according to claim 1, wherein the
piezoelectric element is affixed to the stirring member at least at
a central section in the direction of a rotary shaft of the
stirring member.
5. The developer container according to claim 1, wherein the
piezoelectric element is formed in an elongate shape in a direction
perpendicular to a rotary shaft of the stirring member.
6. The developer container according to claim 1, wherein the
deflection forming portion is part of a wall of the accommodating
portion.
7. The developer container according to claim 1, wherein the
deflection forming portion is a projection that protrudes from a
wall of the accommodating portion, so as to overlap a movement
region of the stirring member, outside the accumulation region.
8. The developer container according to claim 1, wherein the
deflection forming portion is a shaft that is provided parallelly
to a rotary shaft of the stirring member, at a position overlapping
a movement region of the stirring member, outside the accumulation
region.
9. A developing apparatus, comprising: the developer container
according to claim 1; and a developer carrier, provided in an
opening of the developer container, and carrying a developer.
10. A process cartridge for performing an image forming process of
forming an image, by way of a developer, on a recording medium, the
process cartridge being configured so as to be detachably mounted
to an apparatus main body of an image forming apparatus, wherein
the process cartridge comprises the developer container according
to claim 1.
11. An image forming apparatus in which an image is formed by a
developer on a recording medium, the apparatus comprising: the
developer container according to claim 1; voltage detection means
for detecting voltage that is outputted by the piezoelectric
element; and developer residual amount detection means for
detecting a residual amount of the developer that is accommodated
in the accommodating portion, on the basis of a voltage value
detected by the voltage detection means, wherein the developer
residual amount detection means detects the residual amount of the
developer on the basis of a reference voltage value, which is an
output voltage value of the piezoelectric element detected by the
voltage detection means upon occurrence of flexural deformation due
to contact of the stirring member with the deflection forming
portion, and an effective value of an output voltage value of the
piezoelectric element detected by the voltage detection means while
the stirring member is passing through the accumulation region,
from among output voltage values of the piezoelectric element
outputted over one rotation of the stirring member.
12. The developer container according to claim 1, wherein a
residual amount of the developer is detected on the basis of a
signal from the piezoelectric element.
13. The developer container according to claim 1, wherein the
sheet-like stirring member is a flexible member.
14. The developer container according to claim 1, wherein the
piezoelectric element is a film-like element.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a developer container, a
developing apparatus, a process cartridge and an image forming
apparatus.
[0003] 2. Description of the Related Art
[0004] Developing assemblies that are used in image forming
apparatuses such as electrophotographic printers or the like
comprise ordinarily a developer container in which a developer
(toner) is accommodated, and a developing roller, rotatably
provided at an opening of the developer container, and which
carries and transports the developer from inside the developer
container. The developer inside the developer container is stirred
through rotation of a stirring member that is provided inside the
developer container, is transported by the developing roller, and
is consumed thereupon by being used to develop an electrostatic
latent image.
[0005] Herein, Japanese Patent Application Publication No.
H3-271785 discloses, as a method for detecting a residual amount of
the consumed developer from inside the developer container, a
method that involves detecting the pressure (toner powder pressure)
that the developer exerts on the stirring member. In the method
disclosed in Japanese Patent Application Publication No. H3-271785,
the stirring member is provided with a piezoelectric element, such
that the residual amount of the developer is detected on the basis
of changes in the developer pressure exerted on the piezoelectric
element.
SUMMARY OF THE INVENTION
[0006] In the configuration of Japanese Patent Application
Publication No. H3-271785, a plate-like polymer piezoelectric
element is affixed to a paddle surface of a rigid stirring member.
The polymer piezoelectric element detects, in the form of change of
generated voltage, small changes in the pressure that the developer
exerts on a piezoelectric surface, in the thickness direction.
Changes in generated voltage arise as a result of deformation of
the piezoelectric element. Herein, the deformation of the
piezoelectric element derived from developer pressure in the
thickness direction involves only deformation of contracting in the
thickness direction. The resulting deformation amount is very
small, and the changes in generated voltage are likewise extremely
small. Accordingly, the sensitivity of the piezoelectric element,
as a sensor, is very low, and detection precision is limited.
[0007] It is an object of the present invention to provide a
technology that allows enhancing the detection precision of the
residual amount of a developer.
[0008] To attain the above goal, a developer container of the
present invention, comprising:
[0009] an accommodating portion in which a developer is
accommodated;
[0010] a sheet-like stirring member that, by rotating, stirs the
developer accommodated in the accommodating portion;
[0011] a piezoelectric element that is affixed to the stirring
member and that outputs voltage, when being deformed; and
[0012] a deflection forming portion that comes in contact with the
stirring member, thereby causing the stirring member to deflect,
when a free end of the rotating stirring member is outside a
developer accumulation region in the accommodating portion.
[0013] To attain the above goal, a developing apparatus of the
present invention, comprising:
[0014] the developer container; and
[0015] a developer carrier, provided in an opening of the developer
container, and carrying a developer.
[0016] To attain the above goal, a process cartridge of the present
invention for performing an image forming process of forming an
image, by way of a developer, on a recording medium, the process
cartridge being configured so as to be detachably mounted to an
apparatus main body of an image forming apparatus,
[0017] wherein the process cartridge comprises the developer
container.
[0018] To attain the above goal, an image forming apparatus of the
present invention in which an image is formed by a developer on a
recording medium,
[0019] the apparatus comprising:
[0020] the developer container;
[0021] voltage detection means for detecting voltage that is
outputted by the piezoelectric element; and
[0022] developer residual amount detection means for detecting a
residual amount of the developer that is accommodated in the
accommodating portion, on the basis of a voltage value detected by
the voltage detection means, wherein
[0023] the developer residual amount detection means
[0024] detects the residual amount of the developer on the basis
of
[0025] a reference voltage value, which is an output voltage value
of the piezoelectric element detected by the voltage detection
means upon occurrence of flexural deformation due to contact of the
stirring member with the deflection forming portion, and
[0026] an effective value of an output voltage value of the
piezoelectric element detected by the voltage detection means while
the stirring member is passing through the accumulation region,
from among output voltage values of the piezoelectric element
outputted over one rotation of the stirring member.
[0027] The present invention succeeds thus in providing a
technology that allows enhancing the detection precision of the
residual amount of a developer.
[0028] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a schematic diagram illustrating the configuration
of a developer container according to Embodiment 1 of the present
invention;
[0030] FIGS. 2A and 2B are schematic cross-sectional diagrams
illustrating the configuration of a stirring member;
[0031] FIG. 3 is a schematic cross-sectional diagram of a process
cartridge and an image forming apparatus;
[0032] FIGS. 4A and 4B are schematic diagrams illustrating the
configuration of a stirring member in an embodiment of the present
invention;
[0033] FIGS. 5A and 5B are a flowchart of toner residual amount
detection;
[0034] FIGS. 6A to 6F are schematic cross-sectional diagrams of a
developing apparatus, illustrating the progress of a
stirring-circulation process;
[0035] FIG. 7 is a voltage waveform diagram of a piezoelectric
element during rotation of a stirring member in a conventional
example;
[0036] FIG. 8 is a voltage waveform diagram of a piezoelectric
element during rotation of a stirring member in an embodiment of
the present invention;
[0037] FIG. 9 is a diagram illustrating the profile of detection
results of a toner residual amount in a conventional example;
[0038] FIG. 10 is a diagram illustrating the profile of detection
results of toner residual amount in an embodiment of the present
invention;
[0039] FIGS. 11A and 11B are schematic cross-sectional diagrams
illustrating the configuration of a developing apparatus according
to a variation of Embodiment 1 of the present invention; and
[0040] FIGS. 12A and 12B are schematic cross-sectional diagrams
illustrating the configuration of a developing apparatus according
to a variation of Embodiment 2 of the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0041] Now, with reference to the drawings, the implementation of
the present invention will be described below in detail in an
illustrative manner based on embodiments. However, the sizes,
materials, shapes, relative arrangements, and the like of
components described in the embodiments should be appropriately
changed in accordance with the configuration of an apparatus to
which the invention is applied or with any of various conditions.
That is, the scope of the invention is not intended to be limited
to the following embodiments.
Embodiment 1
Schematic Configuration Diagram of an Image Forming Apparatus
[0042] FIG. 3 is a schematic cross-sectional diagram illustrating
the schematic configuration of a process cartridge and an image
forming apparatus according to an embodiment of the present
invention. An example of a laser beam printer of detachable process
cartridge type will be explained in the present embodiment as the
image forming apparatus.
[0043] Herein, the term image forming apparatus
(electrophotographic image forming apparatus) denotes an image
forming apparatus in which an image is formed on a recording
material (recording medium), by a developer (toner), as a result of
an electrophotographic image forming process. Examples of the image
forming apparatus include, for instance, electrophotographic
copiers, electrophotographic printers (LED printers, laser beam
printers and the like), electrophotographic fax machines and
electrophotographic word processors, as well as multifunction
machines (multifunction printers) of the foregoing. The term
recording material denotes a material on which an image is formed,
for instance recording sheets, OHP sheets and the like.
[0044] The term process cartridge denotes a member resulting from
integrating, in the form of a cartridge, an electrophotographic
photoconductor drum and at least one from among a charging device,
a developing means and a cleaning means, as a process means that
acts on the electrophotographic photoconductor drum. This process
cartridge is configured to be detachably mounted to the main body
of the image forming apparatus. In the explanation below, the term
image forming apparatus main body (hereafter "apparatus main body")
denotes an apparatus configuration portion that results from
excluding at least the process cartridge, the developing apparatus
or the developer container from the configuration of the apparatus
main body.
[0045] In FIG. 3, the reference symbol 1 denotes an
electrophotographic photoconductor of rotary drum type, being an
organic photoconductor (OPC) wherein a photoconductor layer
comprising an organic photoconductor layer is formed on the outer
periphery of a grounded cylindrical aluminum substrate. The OPC
photoconductor 1 is rotationally driven, at a predetermined process
speed (peripheral speed) of for instance 200 mm/sec, in the
clockwise direction R1 of the arrow. The reference symbol 2 denotes
a charging roller, as a contact charging member that is brought in
contact with the OPC photoconductor 1. In the case of the present
embodiment, the charging roller 2 is rotationally driven
accompanying the rotational driving of the OPC photoconductor
1.
[0046] In the rotation process thereof, the OPC photoconductor 1
(hereafter, photoconductor 1) undergoes a charging process of being
homogeneously charged, to a predetermined polarity (negative, in
the present embodiment) and predetermined potential, by the
charging roller 2 to which an oscillating voltage (VAC+VDC) is
applied. The charging process surface of the photoconductor 1
undergoes scanning exposure by an exposure device 33, via a mirror
32. A laser beam emitted by the exposure device 33 is modulated in
accordance with a time-series electric digital image signal, of the
intended image information, as outputted by a laser scanner not
shown. An electrostatic latent image corresponding to the intended
image information becomes formed as a result on the surface of the
OPC photoconductor 1.
[0047] Toner negatively charged by a developing sleeve 3 of a
developing apparatus 8 is supplied to the electrostatic latent
image formed on the photoconductor 1, and the electrostatic latent
image becomes reverse-developed thereby. A predetermined developing
bias from a high-voltage power source (not shown) is applied to the
sleeve 3.
[0048] Meanwhile, a recording material (transfer material) 10 is
fed, from a paper feed unit, not shown, to a contact nip section
(transfer section) of the photoconductor 1 and a transfer roller
34, by way of a transfer guide 35, in concert with the timing of
the toner image on the photoconductor 1. The toner image is
transferred from the surface of the photoconductor 1 onto the
surface of the recording material 10. A predetermined transfer bias
from the high-voltage power source is applied to the transfer
roller 34; thereby, the toner image is transferred on account of
the transfer bias. The recording material 10 having passed through
the transfer section is introduced into a fixing apparatus 30. The
toner image undergoes there a fixing process, and is outputted in
the form of an image formed product.
[0049] After transfer of the toner image to the recording material
10, the developer remaining on the photoconductor 1 is removed and
recovered by a cleaning device 6.
[0050] In the present embodiment, four process devices in the above
configuration, namely the photoconductor 1, the charging roller 2,
the developing apparatus 8 and the cleaning device 6 are configured
integrally in the form of the process cartridge 36, so as to be
detachably mounted to an apparatus main body 40 of the image
forming apparatus. The cartridge configuration is not limited to
the configuration disclosed herein, and it suffices that the
cartridge be provided with at least one from among the
photoconductor 1, the charging member 2, the developing apparatus 8
and the cleaning device 6.
[0051] The process cartridge 36 has a slit window hole through
which a laser beam from the exposure device 33 is incident, and an
opening and closing shutter unit (not shown) facing the exposed
section on the underside of the photoconductor 1. These openings
are configured so as to remain closed while the process cartridge
36 is removed from the apparatus main body 40, and to remain open
while fitted to the apparatus main body 40. When the process
cartridge 36 is fitted to the apparatus main body 40, the process
cartridge 36 becomes mechanically and electrically coupled to a
driving mechanism that is provided on the apparatus main body 40
side. As a result, this enables driving of, for instance, the
photoconductor 1 or the developing sleeve 3 of the developing
apparatus 8, and allows a predetermined bias to be applied to the
charging roller 2, the developing sleeve 3 and the like, from a
power source on the apparatus main body 40 side.
[0052] <Developing Apparatus>
[0053] FIG. 1 is a schematic cross-sectional diagram illustrating
the configuration of the developing apparatus according to the
present embodiment. The developing apparatus 8 comprises a
developer container 8a that accommodates toner (developer) 5, the
developing sleeve 3 as a developing roller, an elastic blade 4 as a
developer regulation member, and a stirring member 11 for stirring
the toner 5 inside the developer container 8a. Magnetic toner in
the form of a one-component magnetic developer is used as the toner
5 in the present embodiment.
[0054] The developing sleeve 3 is a non-magnetic developer carrier
having a built-in fixed magnet 31. The developing sleeve 3 is
rotatably provided in an opening, of the developer container 8a,
that is provided at a position opposing the photoconductor 1 (FIG.
3). The developing sleeve 3 comprises, for instance, an aluminum
pipe having a diameter of 14 mm, and rotates at a speed of 205 mm/s
in the counterclockwise direction R2 of the arrow of FIG. 1. Four
alternately disposed magnetic poles N, S, N, S of the fixed magnet
31, have each a magnetic flux density of 75 mT. The toner 5 inside
the developer container 8a is carried, on the developing sleeve 3,
by virtue of the magnetic forces of the magnetic poles N, S, N, S,
and is transported in the R2 direction accompanying the rotation of
the developing sleeve 3.
[0055] The elastic blade 4 is fixed to an opening of the developer
container 8a in such a way so as to come in contact with the
surface of the developing sleeve 3, and regulate the amount of
toner 5 that is carried and transported by the developing sleeve 3.
The elastic blade 4 regulates the thickness of the toner 5 on the
developing sleeve 3, to form a developer layer (toner layer) of a
predetermined thickness. The layer of toner 5 thus formed is
transported, accompanying the rotation of the developing sleeve 3,
to a developing section that is formed by the developing sleeve 3
and the photoconductor 1, to develop the electrostatic latent image
that is formed on the photoconductor 1.
[0056] The stirring member 11 is provided so as to be rotatable
about a rotary shaft 11a. The toner 5 inside the developer
container 8a is loosened and caused to circulate throughout the
interior of the developer container 8a by the rotating stirring
member 11. A configuration is achieved as a result wherein
degradation of the toner 5 is suppressed, and the toner 5 inside
the developer container 8a can be consumed thoroughly.
[0057] The stirring member 11 is a flexible sheet-like member
configured so as to deform on account of resistance from the toner
5 during rotation. Deformation of the stirring member 11 is
detected by a piezoelectric element 12, as a detection member, that
is attached to the stirring member 11. A reference-setting
projection 9, as a deflection forming portion, is provided, inside
the developer container 8a, at a region outside (above) a
accumulation region of the toner 5, in such a manner that the
reference-setting projection 9 can come in contact with the
rotating stirring member 11. The term accumulation region of the
toner 5 denotes herein a region at which most of the toner 5
accumulates in the interior (accommodating portion) of the
developer container 8a in a static manner, without floating up or
splashing, during normal use. The rotary shaft 11a of the stirring
member 11 is preferably in a state of not being buried within the
accumulation region of the toner 5, from the viewpoint of detection
precision. However, the rotary shaft 11a, or the root side of the
stirring member 11, which exhibits a relatively small deformation
amount, may be in a state of being slightly buried within the
accumulation region, so long as deformation of the leading end side
of the stirring member 11, the deformation amount whereof is
relatively large, is not affected thereby, i.e. so long as
detection precision is little affected.
[0058] <Configuration of the Stirring Member and the
Piezoelectric Element>
[0059] An explanation follows next with reference to FIGS. 2A, 2B,
4A and 4B, on the configuration of the stirring member and the
piezoelectric element. FIGS. 2A, 2B are schematic cross-sectional
diagrams illustrating the configuration of the stirring members,
where FIG. 2A illustrates a conventional stirring member and FIG.
2B illustrates the stirring member of the present embodiment. FIGS.
4A, 4B are schematic diagrams illustrating the configuration of the
stirring member of the present embodiment, where FIG. 4A is a
schematic cross-sectional diagram of a piezoelectric element, and
FIG. 4B is a cross-sectional diagram and a front-view diagram
illustrating the configuration of the stirring member. In the
present embodiment, as illustrated in FIGS. 4A, 4B, a sheet-like
member, being a flexible member having an elastic restoring force,
is used as the stirring member 11, such that the thin film-like
piezoelectric element 12 is integrally bonded to the deflection
surface of the stirring member 11, in such a manner so as to
deflect in a rolling direction (i.e. a drawing direction, which is
a direction in which the piezoelectric element is drawn to be
shaped into a thin film by a rolling process) of high
piezoelectricity. The piezoelectric element 12 is affixed to the
stirring member 11, at a surface of the latter opposite that where
the stirring member 11 comes in contact with the reference-setting
projection 9 (upstream side of the stirring member 11 in the
rotation direction thereof), in such a manner that the
piezoelectric element 12 extends in a direction perpendicular to
the rotary shaft 11a of the stirring member 11.
[0060] The stirring member 11 is a sheet-like member made up of a
resin such as polyphenylene sulfide (PPS) or polyethylene
terephthalate (PET). The stirring member 11 has a thickness of 150
.mu.m, so as to be flexible while exhibiting a sufficient elastic
restoring force towards bending stress.
[0061] A piezo film (by Tokyo Sensor Co., Ltd.), which is a polymer
piezoelectric element, is used as the piezoelectric element 12 in
the present embodiment. As illustrated in FIG. 4A, the material of
the piezo film, which has a thickness of 20 .mu.m, is
polyvinylidene fluoride (PVDF). A respective silver ink electrode
is formed on the front and rear faces of the piezoelectric element
12, which is bonded to the insulating stirring member 11 in such a
manner that the rolling direction at the time of production, as the
direction of highest piezoelectricity, is perpendicular to the
stirring rotary shaft. The electrode surfaces of the piezoelectric
element 12 are led out by way of metal films and metal wires, not
shown, and are connected, by way of sliding electrodes, to a
generated voltage detection circuit (peak detection circuit 13 and
an effective value detection circuit 14) of the image forming
apparatus main body.
[0062] In the present embodiment, as illustrated in FIG. 4B, a
piezo film having a width of 10 mm, as the piezoelectric element
12, is bonded to the central section of the stirring member 11, in
the axial direction thereof, in such a manner that the piezo film
is integrated with the stirring member 11. The piezo film is
imparted with an elongate shape in the direction perpendicular to
the rotary shaft 11a of the stirring member 11. The length of the
piezo film in this direction is set, as appropriate, within a range
of 50 to 95 mm, in accordance with product specifications and so
forth. In the configuration illustrated in FIGS. 4A, 4B, the end of
the piezo film is in contact with the rotary shaft 11a of the
stirring member 11, but a gap may be provided between the piezo
film and the rotary shaft 11a. The position at which the piezo film
is affixed in the longitudinal direction is not particularly
limited, but preferably the piezo film is affixed to the stirring
member 11 at the leading end side, where deformation is large. As a
characterizing feature of the piezo film, the latter is flexible
and can be made into a thin film. A small force in the rolling
direction gives rise to large stress within the material of the
piezo film, since the latter is thin and has a very small
cross-sectional area. By virtue of that feature, the piezo film
exhibits very high sensitivity towards elongation in the rolling
direction, as compared with that in the thickness direction, with a
standard effective sensitivity of rolling direction versus
thickness direction of about 1000:1. Toner powder pressure
(developer pressure) can thus be detected with high sensitivity by
exploiting to the maximum such a characteristic of the piezo film.
The sign of the output voltage of the piezo film varies depending
on the rotation direction, the frontward deflection, and the
deflection direction of the stirring member 11.
[0063] As described above, the sheet-like stirring member 11 is
configured in such a manner that the leading end thereof is a free
end that can undergo significant bending deformation. The
piezoelectric element 12, in the form of the piezo film, is
disposed in the stirring member 11 in such a manner that the
piezoelectric element 12 deflects significantly in the rolling
direction, in which the piezoelectricity of the piezo film is
large. As a result, the flexural deformation of the stirring member
11 is converted to a large elongation deformation of the piezo film
in the rolling direction, and hence very small changes in toner
powder pressure can be detected through conversion, into large
voltage changes, by the piezo film having a comparatively small
area.
[0064] <Reference-Setting Projection>
[0065] The reference-setting projection 9 provided inside the
developer container 8a will be explained next. The film-like
piezoelectric element 12 has a temperature characteristic, and thus
the voltage outputted by the piezoelectric element 12, on account
of deflection of the stirring member 11, may in some instances vary
significantly depending on differences in environmental
temperature. The piezoelectric element 12 is film-like and is hence
prone to exhibit large variability in mounting precision. This
variability when the piezoelectric element 12 is bonded exerts in
turn an influence on sensitivity, and the output voltage may vary
significantly as a result. The purpose of the reference-setting
projection 9 is to deliberately bring about a deflection state
while the stirring member 11 is in a state of not being influenced
by toner powder pressure, so as to detect the toner powder
pressure, taking as a reference the output voltage value detected
by piezoelectric element 12 at that time. The reference-setting
projection 9 protrudes beyond the wall of the developer container
8a, so as to overlap with the movement region of the stirring
member 11, outside the accumulation region of the toner 5 in the
interior of the developer container 8a.
[0066] In the present embodiment, the reference-setting projection
9 is provided at the top of the interior of the developer container
8a, as illustrated in the figures. The reason for providing the
reference-setting projection 9 at the top of the developer
container 8a is to cause the piezoelectric element 12 to output a
reference voltage value, by imparting deflection to the stirring
member 11 and the piezoelectric element 12, while the latter are
unaffected by the toner inside the container. Using this reference
voltage value allows correcting the output voltage value of the
piezoelectric element 12, even upon changes in the sensitivity
thereof, derived from environmental fluctuations or the like, as
described above.
[0067] In the present Embodiment 1, the reference-setting
projection 9 that protrudes down from the ceiling of the developer
container 8a is provided for obtaining a reference voltage value,
but the embodiment does not necessarily need to resort to a
configuration where such a projection is provided. FIGS. 11A, 11B
illustrate configurations of variations in which the configuration
of the reference-setting projection 9 is modified. For instance,
part of the ceiling of the developer container 8a may be lowered,
to form a portion 8b that comes in contact with the stirring member
11, as illustrated in FIG. 11B. Various configurations can thus be
adopted, so long as the reference-setting projection 9 can come in
contact with the stirring member 11, and the latter can deflect
while unaffected by the toner. The height and width of the
reference-setting projection 9 (dimension in a direction
perpendicular to the paper in FIG. 1) are set as appropriate in
accordance with, for instance, the specifications of the stirring
member 11 and the developer container 8a. The width of the
reference-setting projection 9 may be identical to or different
from the width of the stirring member 11. Further, a configuration
may be resorted to wherein the reference-setting projection 9 is
provided as a plurality thereof, in the abovementioned width
direction. In this case, for instance, projections 9a, 9b of
mutually different height may be arrayed as illustrated in FIG.
11A, in such a manner that the stirring member 11 having come in
contact with the projections 9a, 9b is brought to specific
deformation states. A configuration can be adopted herein, as
appropriate, that allows eliciting a desired flexural deformation
in the stirring member 11.
[0068] <Toner Residual Amount Detection Method>
[0069] FIGS. 5A, 5B are flowcharts of toner residual amount
detection, where FIG. 5A is a flowchart of the present embodiment,
and FIG. 5B is a flowchart of a conventional example. FIGS. 6A to
6F are schematic cross-sectional diagrams of a developing
apparatus, and illustrate the progress of a stirring-circulation
process in a conventional example and in the present embodiment.
FIG. 6A to FIG. 6C illustrate a stirring-circulation process in a
conventional example, and FIG. 6D to FIG. 6F illustrate a
stirring-circulation process in the present embodiment. FIG. 7 is a
diagram illustrating a voltage waveform that is generated by the
piezoelectric element upon rotation of the stirring member in a
conventional example. FIG. 8 is a diagram illustrating a voltage
waveform generated by the piezoelectric element upon rotation of
the stirring member in the present embodiment.
Conventional Example
[0070] As illustrated in FIG. 5B, toner residual amount detection
is configured so as to be activated upon turning on of a main body
power source, or upon returning from a main body paused state
(S21). Upon turning on of the main body power source or upon return
from a main body power source, a preparatory operation in which the
stirring member 11 is rotated is executed prior to printing (S22).
In the rotational operation of the stirring member there is
detected the voltage generated by the piezoelectric element (piezo
film) 12, to detect the toner residual amount.
[0071] As illustrated in FIG. 6A, the stirring member 11 starts
rotating, clockwise in the figure, from a position outside the
toner, and thereafter, the stirring member 11 plunges into the
toner agent surface, as illustrated in FIG. 6B; thereby, the
stirring member 11 undergoes flexural deformation such that the
amount of deflection changes (increases) gradually. The amount of
flexural deformation of the stirring member 11 increases in the
counterclockwise direction (negative direction) in the figure, and
the voltage generated in the piezoelectric element 12 changes in
response thereto. The amount of deflection of the stirring member
11 increases little by little, and reaches eventually a maximum
amount of deflection. Thereafter, the amount of deflection
decreases gradually, and then deflection of the stirring member 11
is released sharply as the stirring member 11 emerges from the
toner agent surface, as illustrated in FIG. 6C. The stirring member
11 deforms then sharply in the back-deflection direction (positive
direction), and hence the piezoelectric element 12 outputs a
voltage that exhibits a large change from negative to positive, as
illustrated in FIG. 7, corresponding to the change in the
deflection direction and deformation with an abrupt amount of
deflection.
[0072] An effective value Vave of a serial output waveform
generated in the stirring period is detected by an effective value
detection circuit (S23). Thereafter, a CPU determines a toner
residual amount on the basis of a relationship, prepared
beforehand, between the toner residual amount and the output
voltage of the piezoelectric element 12 (S24). The CPU notifies the
residual amount to a user (S25), and brings the image forming
apparatus to a printing queue state (S26).
Present Embodiment
[0073] In the present embodiment a toner residual amount is
detected by using a voltage peak value generated by the
piezoelectric element 12 when the stirring member 11 contacts the
reference-setting projection 9, and a voltage effective value that
is generated by the piezoelectric element 12 while the stirring
member 11 is immersed in the toner. In the present embodiment, a
voltage detection means in the form of the peak detection circuit
13 and the effective value detection circuit 14 is connected to the
piezoelectric element 12, such that a CPU 15, as a developer
residual amount detection means, detects the toner residual amount
on the basis of voltage values outputted by these circuits. The CPU
15 is also a control means for controlling the various operations
of the image forming apparatus. The image forming apparatus is
provided with a storage means in the form of a ROM, a RAM and the
like, such that the CPU 15 performs various control processes by
drawing on information stored in these memories and that is
necessary for various computations.
[0074] The operating conditions in toner residual amount detection
are identical to those in the above-described conventional
configuration, as illustrated in FIG. 5A. Accordingly, toner
residual amount detection is activated upon turning on of the main
body power source, or upon return from a paused state (S11). Upon
turning on of the main body power source or upon return from a main
body power source, a preparatory operation of rotating the stirring
member 11 is executed prior to printing (S12). Herein there is
detected the voltage value generated during this rotational
operation in the piezoelectric element 12, and equivalent to one
rotation of the stirring member 11. To detect the toner residual
amount, there are detected a voltage peak value Vmax generated by
the piezoelectric element 12 upon contact of the stirring member 11
with the reference-setting projection 9, and the effective value
Vave that is an average voltage value of the output voltage value
generated by the piezoelectric element 12 while the stirring member
11 is immersed in the toner, over one rotation.
[0075] As illustrated in FIG. 6D, the stirring member 11 comes in
contact with the reference-setting projection 9, from a position
outside the toner, immediately after start of the rotation. The
stirring member 11 is caused thereupon to sharply undergo
significantly deflection, as a result of which the piezoelectric
element 12 generates a large peak output voltage Vmax. The peak
detection circuit 13 detects this voltage as the reference-setting
peak voltage Vmax (S13). Thereafter, the stirring member 11 plunges
into the toner agent surface, as illustrated in FIG. 6E, and
undergoes flexural deformation. The amount of deflection of the
stirring member 11 increases, along with the rotation, in the
counterclockwise direction (negative direction) in the figure, and
the voltage generated in the piezoelectric element 12 changes in
response thereto. The amount of deflection of the stirring member
11 increases little by little, and reaches eventually a maximum
amount of deflection. Thereafter, the amount of deflection
decreases gradually, and then deflection of the stirring member 11
is released suddenly as the stirring member 11 emerges from the
toner agent surface, as illustrated in FIG. 6F. The stirring member
11 deforms then sharply in the back-deflection direction (positive
direction), and hence the piezoelectric element 12 outputs a
voltage that exhibits a large change from negative to positive, as
denoted by H in FIG. 8, corresponding to the change in the
deflection direction and the sharp variation in the amount of
deflection.
[0076] The effective value detection circuit 14 detects the
effective value Vave within a range in the serial output waveform
that are generated in one period T of stirring (see FIG. 8), while
the stirring member 11 is immersed in the toner (while passing
through the toner accumulation region), that does not include a
region at which the peak voltage occurs (S14). Thereafter, the CPU
15 computes a value (Vave/Vmax) resulting from dividing the
effective value by a reference-setting peak value (S15), and
determines a toner residual amount on the basis of a relationship,
prepared beforehand, between the toner residual amount and the
output voltage of the piezoelectric element 12 (for instance, a
table such as the one illustrated in FIG. 10) (S16). The CPU 15
notifies the toner residual amount to the user, by way of a
notification means 16 (S17), and brings the image forming apparatus
to a printing queue state (S18).
[0077] The reason for computing Vave/Vmax will be explained next.
The temperature-voltage output characteristic of the film-like
piezoelectric element 12 exhibits a substantially linear
proportional relationship. Accordingly, a rise in temperature
translates into a rise also of the effective value that is used in
residual amount detection, which may preclude accurate residual
amount detection. In some instances, moreover, the sensitivity may
vary depending on the way in which the piezoelectric element 12 is
mounted to the stirring member 11, such that the signal of residual
amount detection exhibits variability for identical toner residual
amounts. Accordingly, the outputted voltage values are normalized
(Vave/Vmax) using a peak voltage value as a reference, to enable
thereby residual amount detection excluding the influence of error
derived from temperature changes and element mounting.
[0078] The timing of the residual amount detection in the present
embodiment is designated as described above, but the detection
timing is not particularly limited. The detection timing may be
immediately before or immediately after the printing operation, but
is preferably other than during printing. In the present
embodiment, the toner residual amount is determined through
sampling of output values at each period T of stirring, but any
period may be relied upon for sampling, so long as the peak value
derived from the reference-setting projection 9 can be compared
with an effective value associated with the toner residual
amount.
Comparative Experiment Between a Conventional Example and the
Present Embodiment
[0079] A durability experiment according to a conventional residual
amount detection method and the residual amount detection method of
the present embodiment was performed in order to compare the
foregoing two methods. The durability test conditions included
environment conditions of 10.degree. C., 20.degree. C. and
30.degree. C., under which there was measured a profile of the
toner residual amount as detected in accordance with the respective
method. The experiment results are illustrated in FIG. 9 and FIG.
10. Herein, FIG. 9 is a diagram illustrating the profile of the
toner residual amount as detected in accordance with a residual
amount detection method of a conventional example, and FIG. 10 is a
diagram illustrating the profile of the toner residual amount as
detected in accordance with the residual amount detection method of
Embodiment 1 of the present invention.
[0080] In a conventional method, as illustrated in FIG. 9, the
output value of the piezoelectric element with respect to the toner
residual amount exhibited different results depending on
differences in environmental temperature. It is found that output
values are higher when the environmental temperature is high, and
that it is thus difficult to detect an accurate toner residual
amount, due to differences in environmental temperature. In the
present embodiment, by contrast, variability derived from
environmental temperature is small, and computation results based
on the toner residual amount and the output of the piezoelectric
element evolve in the same way for any environment, as illustrated
in FIG. 10. Accordingly, variability derived from environmental
fluctuations and the like is small, and the toner residual amount
can be detected with good precision.
Embodiment 2
[0081] A developer container according to Embodiment 2 of the
present invention will be explained next with reference to FIGS.
12A, 12B. Herein, FIGS. 12A, 12B are schematic cross-sectional
diagrams illustrating the configuration of a developing apparatus
according to the present embodiment, where FIG. 12A illustrates a
schematic cross-sectional diagram of the developing apparatus of
Embodiment 1, and FIG. 12B illustrates that of Embodiment 2. Only
features different from those of Embodiment 1 will be explained
herein. Features shared with Embodiment 1 will be denoted by the
same reference symbols, and will not be explained again. Subject
matter not explained herein is identical to that in Embodiment
1.
[0082] In a configuration where part of the wall of the developer
container 8a, such as the reference-setting projection 9 of
Embodiment 1, is caused to protrude, a toner jam may arise at the
reference-setting position, as illustrated in FIG. 12A, due to
scattering of toner when the stirring member 11 emerges from the
toner agent surface. Such a toner jam may affect reference-setting
detection.
[0083] As a characterizing feature of Embodiment 2, a reference
shaft 17 that extends in the longitudinal direction of the
developer container 8a (direction perpendicular to the paper in
FIG. 12) is provided, as illustrated in FIG. 12B, instead of the
reference-setting projection 9 of Embodiment 1. The reference shaft
17 is provided parallelly to the rotary shaft of the stirring
member 11, at a position that overlaps the movement region of the
stirring member 11, outside the accumulation region of the toner 5
within the developer container 8a. By virtue of such a
configuration, a high-precision reference voltage can be detected,
without toner jamming at the reference-setting position, even when
toner scattering occurs when the stirring member 11 emerges from
the toner agent surface.
[0084] The configuration for preventing splattered toner from
remaining at the reference-setting position is not limited to
providing the reference shaft 17, as in the present embodiment. For
instance, an effect identical to that of the present embodiment may
be accomplished by providing through-holes in the reference-setting
projection 9 of Embodiment 1, such that splattering toner can pass
through the holes.
[0085] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0086] This application claims the benefit of Japanese Patent
Application No. 2013-229714, filed on Nov. 5, 2013, which is hereby
incorporated by reference herein in its entirety.
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